Optical Coherence Tomography (OCT) is a technique for performing high resolution cross-sectional imaging that can provide images of tissue structure on the micron scale in situ and in real time [Huang, D., E. A. Swanson, et al. Science 254 (5035): 1178-81]. OCT is a method of interferometry that determines the scattering profile of a sample along the OCT beam. Each scattering profile is called an axial scan, or A-scan. Cross-sectional images, and by extension 3D volumes, are built up from many A-scans, with the OCT beam moved to a set of transverse locations on the sample. Motion of the sample with respect to the OCT scanner will cause the actual locations measured on the sample to be arranged differently than the scan pattern in scanner coordinates, unless the motion is detected and the OCT beam placement corrected to track the motion.
In recent years, frequency domain OCT techniques have been applied to living samples [Nassif, N. A., B. Cense, et al. Optics Express 12(3): 367-376]. The frequency domain techniques have significant advantages in speed and signal-to-noise ratio as compared to time domain OCT [Leitgeb, R. A., et al. Optics Express 11(8): 889-894; de Boer, J. F. et al. Optics Letters 28; 2067-2069; Choma, M. A. and M. V. Sarunic Optics Express 11: 2183-2189]. The greater speed of modern OCT systems allows the acquisition of larger data sets, including 3D volume images of human tissue.
In the case of ophthalmology, a typical patient can comfortably hold his eye open for a few seconds. OCT systems can advantageously use these few seconds to collect extensive images [Hitzenberger, C. K. et al. “Three-dimensional imaging of the human retina by high-speed optical coherence tomography.” Optics Express 11(21): 2753-2761, and “Spectral Radar: Optical Coherence Tomography in the Fourier Domain”, Lindner, M. W., Andretzky, P., Kiesewetter, F., and Häusler, G. in B. E. Bouma and G. J. Tearney, Handbook of optical coherence tomography (Marcel Dekker, New York, 2002)].
Various approaches have been developed for analyzing and the displaying information obtained from OCT methods. For example, in U.S. patent application Ser. No. 11/223,549, filed Sep. 9, 2005 (and incorporated herein by reference) a method is disclosed for generating elevation maps or images of a tissue layer/boundary with respect to the location of a fitted reference surface, comprising the steps of finding and segmenting a desired tissue layer/boundary; fitting a smooth reference surface to the segmented tissue layer/boundary; calculating elevations of the same or other tissue layer/boundary relative to the fitted reference surface; and generating maps of elevation relative to the fitted surface.
The subject application relates to additional display methods which will facilitate the diagnosis and treatment of pathologies in the eye of a patient.